JP2018059106A - Non-aqueous inkjet ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-aqueous inkjet ink suitable for printing mainly on a vinyl chloride base material, which has excellent printing performance such as stability in continuous discharge and good storage stability and can give a printed matter excellent in glossiness and durability.SOLUTION: The non-aqueous inkjet ink comprises an organic solvent, a pigment, and a vinyl chloride-vinyl acetate copolymer resin. The vinyl chloride-vinyl acetate copolymer resin has a weight average absolute molecular weight (|Mw|) of 20,000 to 40,000, and a ratio (|Mw|/|Mn|) of the weight average absolute molecular weight to a number average absolute molecular weight (|Mn|) of 1.3 or more and 2.2 or less; and the vinyl chloride-vinyl acetate copolymer resin is an emulsion polymerization product of vinyl chloride monomers and vinyl acetate monomers.SELECTED DRAWING: None

Description

  The present invention has excellent printing performance such as continuous discharge stability, has good storage stability, and can obtain a printed matter with excellent gloss and durability, and is suitable mainly for printing on a vinyl chloride substrate. The present invention relates to a non-aqueous inkjet ink.

  The ink jet recording method is a recording method in which characters and images are obtained by ejecting ink droplets directly from a very fine nozzle onto a recording member and attaching them. According to this method, there is an advantage that not only the noise of the apparatus to be used is small and the operability is good, but also colorization is easy and plain paper can be used as a recording member. It is widely used as an output machine in offices and homes.

  On the other hand, in industrial applications, it is used as an output device for digital printing by improving inkjet technology, and non-aqueous (solvent type, UV type) inkjet inks can be printed on plastic substrates such as vinyl chloride (PVC) and PET. Possible printing presses are actually commercially available.

  Solvent-type non-aqueous ink-jet inks are mainly used for printing on PVC substrates, and are mainly used outdoors, so the gloss and durability of printed matter are very important. The gloss and resistance of printed materials mainly depend on the binder resin in the ink. As the binder resin, acrylic resin and vinyl chloride-vinyl acetate copolymer resin (hereinafter also referred to as “vinyl chloride resin”) are widely used. (Patent Documents 1 and 2). Patent Document 3 discloses an ink-jet ink containing a vinyl acetate resin having a specific molecular weight distribution and a polyalkylene glycol dialkyl ether solvent in order to improve the alcohol resistance and continuous discharge stability of a printed material.

JP 2005-105126 A JP 2014-062163 A JP, 2015-067673, A

  However, while maintaining the gloss and durability of the printed material, it is possible to achieve both continuous discharge stability, performance such as mist (a phenomenon in which fine droplets other than the main droplets adhere to the substrate), and ink storage stability. Was difficult. In addition, as a specific phenomenon related to continuous ejection stability, when printing for a long time, “nozzle missing” in which an image is missing due to nozzle clogging, or ink-jet ink droplets do not land at a desired position. There is “deflection”. For example, in Patent Document 3 described above, deflection is generated by continuing printing, and it has been difficult to continuously obtain high-quality images.

  Molecular weight is a major factor related to the physical properties of vinyl chloride resin, but the relative molecular weight in GPC (gel permeation chromatography) in terms of polystyrene has been conventionally used. However, in the case of such relative molecular weights, the amount of high molecular weight components and gel components in the resin cannot be accurately measured due to the difference between the resin structure and the standard material polystyrene and the effect of column adsorption. Therefore, it cannot be said to be a value reflecting the actual state of the resin, and is insufficient to see the relationship between the molecular weight and the physical properties of the resin.

  The present invention has been made in view of the above problems, and is excellent in printing performance such as continuous discharge stability, has good storage stability, and can obtain a printed matter having excellent gloss and durability. An object is to provide a non-aqueous inkjet ink suitable for printing on a vinyl substrate.

That is, the present invention is a non-aqueous inkjet ink containing an organic solvent, a pigment, and a vinyl chloride-vinyl acetate copolymer resin,
The vinyl chloride-vinyl acetate copolymer resin has a weight average absolute molecular weight (| Mw |) of 20,000 to 40,000, and a ratio of the weight average absolute molecular weight to the number average absolute molecular weight (| Mn |). (| Mw | / | Mn |) is 1.3 or more and 2.2 or less,
The vinyl chloride-vinyl acetate copolymer resin is an emulsion polymer of a vinyl chloride monomer and a vinyl acetate monomer.

  Further, the present invention is characterized in that the vinyl chloride-vinyl acetate copolymer resin does not contain a resin having an absolute molecular weight (| M |) of 200,000 or more or is contained in 10% or less of the total resin. The present invention relates to a water-based inkjet ink.

Furthermore, this invention relates to the said non-aqueous inkjet ink characterized by the organic solvent containing any one or more of the solvent represented by general formula (a)-general formula (d).
R ₁ CO (OR ₂ ) _Z OR ₃ (a)
R ₄ CO (OR ₅ ) _Z OCOR ₆ (b)
R ₇ (OR ₈ ) _Z OR ₉ (c)
R ₁₀ COOR ₁₁ (d)

In the above formula, R ₂ , R ₅ and R ₈ are each independently selected from ethylene group, propylene group and butylene group, and R ₁ , R ₃ , R ₄ and R ₆ are each independently selected. An alkyl group having 1 to 4 carbon atoms, R ₇ and R ₉ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ₁₀ is a 2-hydroxyethyl group, and R ₁₁ is 1 carbon atom. -The alkyl group of -8, Z represents the integer of 1-3.

  Furthermore, the present invention relates to the non-aqueous inkjet ink, wherein the organic solvent further contains a nitrogen-containing, sulfur-containing, or lactone solvent.

  Furthermore, the present invention relates to the non-aqueous inkjet ink described above, further comprising a pigment dispersant.

  According to the present invention, it is excellent in printing performance such as continuous discharge stability, has good storage stability, and can obtain a printed matter having excellent gloss and durability, and is suitable mainly for printing on a vinyl chloride substrate. It has become possible to provide a non-aqueous inkjet ink.

  Hereinafter, the present invention will be described with reference to preferred embodiments. In the present invention, “non-aqueous” means that water is not intentionally added. For example, if it is 5% by weight or less with respect to the total amount of the non-aqueous inkjet ink, There is no problem even if moisture is absorbed.

  In the present invention, the vinyl chloride-vinyl acetate copolymer resin used in the non-aqueous inkjet ink is an emulsion polymer of a vinyl chloride monomer and a vinyl acetate monomer, and its weight average absolute molecular weight (| Mw |) is 20 And the ratio (| Mw | / | Mn |) of the weight average absolute molecular weight and the number average absolute molecular weight (| Mn |) is 1.3 or more and 2.2 or less. Features.

  As explained in the prior art, in order to correspond to the PVC base material which is the main target base material of the solvent-type non-aqueous inkjet ink, it is excellent in gloss and resistance of the printed matter, and further, the adhesion to the PVC base material. The use of vinyl chloride-vinyl acetate copolymer resin is essential.

  As a method for synthesizing these vinyl chloride resin, a suspension polymerization method and an emulsion polymerization method are known.

  Among these, the suspension polymerization method uses a vinyl chloride, vinyl acetate, and, if necessary, a mixture of monomers copolymerizable (hereinafter referred to as “vinyl chloride monomer”), the vinyl chloride monomer. In this method, a polymerization initiator, a dispersant, an emulsifier, a stabilizer, and the like soluble in a polymer are added, dispersed in a dispersion medium by a dispersing machine such as a homogenizer, and homogenized and then polymerized. This is a polymerization method generally used in industrial production because water is mainly used as the dispersion medium, the synthesis temperature is easily adjusted, and the polymer can be easily taken out. However, the dispersant and stabilizer are easily dissolved and remain in the product, and when used in inkjet ink, the insoluble component is clogged or adhered to the inkjet head, so that continuous ejection stability is improved. It will get worse. Further, the molecular weight distribution of the obtained polymer is likely to be widened, which also adversely affects the continuous discharge stability, which is not preferable.

  On the other hand, in the emulsion polymerization method, a vinyl chloride monomer is emulsified by adding it to a medium (water) together with an emulsifier such as sodium lauryl sulfate and sodium dodecylbenzenesulfonate, and then a water-soluble polymerization initiator such as ammonium persulfate is added. In addition, it is a method of polymerizing. Since the polymerization reaction proceeds at a high speed, water is used as a main medium, and the synthesis temperature is easy to adjust, it can be said that the synthesis method is also suitable for industrial production. Further, the emulsion polymerization method is preferable in the present invention because the amount of insoluble matter is small compared to the suspension polymerization method, and a polymer having a relatively narrow molecular weight distribution can be obtained by using a chain transfer agent in combination. Selected.

  On the other hand, the vinyl chloride resin produced by the emulsion polymerization method has a problem that it is easy to obtain a polymer having a high degree of polymerization as a whole. As is well known in the art, the molecular weight of a binder resin, such as a vinyl acetate resin, contained in an inkjet ink has a great influence on the continuous ejection stability, the gloss and resistance of printed matter. In other words, it is essential to know the molecular weight characteristics of the binder resin accurately in order to grasp the various characteristics of the inkjet ink using the binder resin.

  Based on the above viewpoints, the present inventors have conducted intensive studies. As a result, even when the polyvinyl chloride resin has the same relative molecular weight characteristics obtained by a general polystyrene-equivalent GPC (gel permeation chromatography) method, the continuous discharge stability is improved. It turned out that a big difference arises in superiority and inferiority. As a result of further investigation, it was found that the superiority or inferiority of the continuous discharge stability is greatly correlated with the absolute molecular weight characteristics of the vinyl chloride resin.

  Specifically, | Mw | of the vinyl chloride-vinyl acetate copolymer resin is 20,000 to 40,000, and | Mw | / | Mn | is 1.3 or more and 2.2 or less. Thus, it has been found that not only the continuous discharge stability is extremely excellent, but also an ink-jet ink having good gloss and resistance of the printed matter and further excellent ink storage stability can be obtained.

  In this specification, the weight average absolute molecular weight, the number average absolute molecular weight, and the absolute molecular weight (| M |) are the weight average molecular weight determined by the gel permeation chromatography multi-angle light scattering (hereinafter GPC-MALS) method, Number average molecular weight and molecular weight are represented. Specifically, a TSKgel column (manufactured by Tosoh Corporation) and a GPC equipped with a multi-angle light scattering detector (manufactured by Wyatt, miniDawn TREOS) (Waters, Alliance GPC) are used, and THF is used as a developing solvent. The absolute molecular weight of the resin itself can be obtained instead of the polystyrene conversion value (relative value) obtained by the conventional GPC method.

  In the GPC-MALS method, since it is not affected by the resin structure or column adsorption, it can accurately measure the amount of the high molecular weight component or gel component in the resin, which greatly affects the continuous discharge stability. It becomes a measurement value that cannot be predicted from the measurement result of the relative molecular weight. Thus, the absolute molecular weight, which is a value reflecting the state of the resin, is a particularly suitable method for examining the relationship with various physical properties.

  In addition, as long as the present inventors investigated, the above-mentioned suitable | Mw | and | Mw | / | Mn | (hereinafter collectively referred to as “preferable absolute molecular weight distribution”) may be applied to commercially available emulsion polymerization products of vinyl chloride resin. These characteristics have been found for the first time in the present invention. Conventionally, commercially available vinyl chloride resins are often those whose molecular weight and molecular weight distribution, which are relative values, are measured by a general polystyrene conversion GPC method, and are not recognized for the above high molecular weight components and gel components, It is considered that the component is sold without being removed.

  Subsequently, each main component of the present embodiment will be described below.

[Binder resin]
| Mw | of the vinyl chloride-vinyl acetate copolymer resin of the present invention needs to be 20,000 to 40,000 as described above, preferably 20,000 to 35,000, and 25,000. Particularly preferred is ˜30,000. Within this range, it is possible to obtain an inkjet ink excellent in continuous discharge stability, gloss and resistance of printed matter, and ink storage stability. | Mw | / | Mn | needs to be 1.3 or more and 2.2 or less, more preferably 1.4 or more and 2.1 or less, and more preferably 1.5 or more and 2.0 or less. Particularly preferred. If it is in this range, nozzle omission of the ink-jet ink can be suppressed, and the continuous ejection stability can be further enhanced.

  Further, in the vinyl chloride-vinyl acetate copolymer resin, the content of the resin having an absolute molecular weight (| M |) of 200,000 or more is preferably 0 to 10% by weight in the total amount of the copolymer resin. It is more preferably ˜5% by weight, particularly preferably 0% by weight. In the above, “0 wt%” means that the target component is not included. Further, among the resins having a content of | M | of 200,000 or more and 0% by weight, | M | does not contain a resin of 150,000 or more, or 10% by weight or less of the total amount of the copolymer resin. It is most preferable to contain. By reducing the blending amount of the high absolute molecular weight component to the above range, it is possible to obtain an ink-jet ink having extremely excellent continuous ejection stability. In addition, the content rate of a certain | M | or more resin is calculated by calculating the area from a graph of molecular weight distribution measured by GPC-MALS.

  In the present invention, as described above, a vinyl acetate resin obtained by an emulsion polymerization method is used to obtain a resin having a suitable absolute molecular weight distribution. In emulsion polymerization, it is preferable to use a polymerization initiator having an ionic group at the terminal. Further, from the viewpoint of reducing environmental burden, it is preferable that no organic chlorine compound is contained as a raw material for emulsion polymerization.

  In emulsion polymerization, as a method for keeping | Mw | and | Mw | / | Mn | of a vinyl chloride-vinyl acetate copolymer resin within the above-mentioned preferable range, for example, adjusting the kind and amount of a chain transfer agent or an emulsifier. , Adjusting the amount and ratio of vinyl chloride and vinyl acetate, and combinations thereof.

  Specifically, the blending amount of the chain transfer agent is, for example, 1.8 to 2.5% by weight, preferably 2.0 to 2.3% by weight, based on the total amount of the vinyl chloride monomer. The emulsion formed in the medium becomes smaller, and as a result, | Mw | and | Mw | / | Mn | of the vinyl chloride-vinyl acetate copolymer resin are suitable.

  In addition, the vinyl acetate ratio in the vinyl chloride-vinyl acetate copolymer resin is preferably 10 to 25% by weight in order to keep the absolute molecular weight distribution more suitable for the ratio of vinyl chloride and vinyl acetate. It is more preferable to set it as weight%, and it is still more preferable to set it as 14-20 weight%. By setting the ratio of vinyl acetate within the above range, | Mw | and | Mw | / | Mn | are not only within the preferable range, but also an inkjet ink having excellent gloss and solvent resistance of the printed matter is obtained. be able to.

  In addition, as described above, there is no commercially available emulsion polymerized vinyl chloride-vinyl acetate copolymer resin having a suitable absolute molecular weight distribution in the present invention. For example, an ultrasonic treatment device or a media disperser is used. By doing this, the vinyl chloride-vinyl acetate copolymer chain is cleaved, and even a commercially available product can be made into a vinyl chloride resin having a suitable absolute molecular weight distribution.

  When using an ultrasonic treatment device, after preparing a solution in which an emulsion polymerization product of a commercially available vinyl chloride-vinyl acetate copolymer resin is dissolved in an organic solvent used in a non-aqueous inkjet ink, an ultrasonic wave is applied to the solution. A method of performing the treatment is preferable. Ultrasonic treatment An ultrasonic homogenizer is preferably used as the apparatus. In addition, in order to fit in said suitable absolute molecular weight distribution, it is preferable that the frequency of an ultrasonic wave is 10-30 kHz, and it is preferable that it is 20-60 micrometers as an amplitude range.

  When the vinyl chloride-vinyl acetate copolymer resin suitable for the present invention is prepared by the above method, commercially available products that can be specifically used include VINNOL (registered trademark) E15 / 45, E15 manufactured by Wacker Chemie. / 45M, E15 / 40M, E15 / 48A, E22 / 48A, E15 / 40A TF, E15 / 45M TF, E15 / 45TF and the like. Among these, VINNOL E15 / 45, E15 / 45M, E15 / 40M, and E15 / 48A are preferable from the viewpoint that the absolute molecular weight distribution can be easily contained in a suitable one and a non-aqueous inkjet ink excellent in continuous discharge stability can be obtained. In consideration of the durability of printed matter, VINNOL E15 / 45 and E15 / 45TF are particularly preferable. Both VINNOL E15 / 45 and E15 / 45TF are produced by an emulsion polymerization method and contain about 85% by weight of vinyl chloride and about 15% by weight of vinyl acetate based on the total amount of the resin.

  In both the case of synthesizing vinyl chloride-vinyl acetate copolymer resin and the case of using a commercially available product, as the vinyl chloride monomer constituting the resin, in addition to vinyl chloride and vinyl acetate, for example, maleic It may contain an acid or vinyl alcohol.

  Moreover, as content of the vinyl chloride-vinyl acetate copolymer contained in the non-aqueous inkjet ink of this invention, 0.5 to 20 weight% is preferable with respect to the nonaqueous inkjet ink whole quantity, and 1 to 10 weight% is more. 2 to 8% by weight is preferable. By setting it as the said range, higher continuous discharge stability can be exhibited.

  In the present invention, other resins can be used in combination with the binder resin for the purpose of improving the adhesion to the substrate and the coating film resistance. The binder resin used in the present invention is not limited as long as it exhibits functions such as abrasion resistance, solvent resistance, stretchability, glossiness, and general versatility of the ink coating film. For example, acrylic resin, styrene-acrylic resin, styrene-maleic acid resin, rosin resin, rosin ester resin, ethylene-vinyl acetate resin, petroleum resin, coumarone indene resin, terpene phenol resin, phenol Resin, urethane resin, melamine resin, urea resin, epoxy resin, cellulose resin, xylene resin, alkyd resin, aliphatic hydrocarbon resin, butyral resin, maleic acid resin, fumaric acid resin, ketone resin, aldehyde resin, etc. Resins that are commonly used can be used. These binder resins may be used alone or in combination of two or more.

  In the present invention, it is preferable to use at least one selected from an acrylic resin, a styrene-acrylic resin, and a styrene-maleic acid resin in addition to the vinyl chloride-vinyl acetate copolymer resin as the binder resin. . The acrylic resin refers to a resin obtained by polymerizing (meth) acrylic acid or (meth) acrylic acid ester. Further, the styrene-acrylic resin and the styrene-maleic acid resin include styrene, maleic acid, etc. within a range not exceeding 50% by weight in the components of the resin, with the remainder being (meth) acrylic acid or ( It is a resin composed of (meth) acrylic acid ester. Examples of suitable components constituting the resin include (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. , Dodecyl (meth) acrylate, hydroxyethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, benzyl (meth) acrylate, styrene, maleic acid and the like. In the present invention, from the viewpoint of the solubility of the resin in the ink and the durability of the printed matter, it is preferably a resin containing methyl methacrylate and butyl methacrylate as a constituent component, and more preferably a resin containing acrylic acid. preferable. In the above, “(meth) acryl” means at least one selected from “acryl” and “methacryl”.

  When an acrylic resin is used in combination in the present invention, it is naturally preferable to have a suitable absolute molecular weight distribution. The acrylic resin preferably used has a weight average absolute molecular weight of 4,000 to 50,000, and within this range, it is possible to obtain a printed material having high resistance without causing mist during printing. More preferably, it is 10,000-45,000, More preferably, it is 15,000-40,000.

  Moreover, as an acrylic resin suitably used, the content of a resin having an absolute molecular weight of 200,000 or more is preferably 10% or less, more preferably 5% or less in all acrylic resins, and not contained at all. Is particularly preferred.

  Furthermore, it is preferable that the acid value of an acrylic resin is 0-30 mgKOH / g. Within this range, high alcohol resistance can be exhibited. More preferably, it is 0-20 mgKOH / g, More preferably, it is 0-15 mgKOH / g. Here, the “acid value” represents an acid value per gram of the acrylic resin, and can be determined by potentiometric titration according to JIS K 0070.

  The glass transition point of the acrylic resin is preferably 40 to 150 ° C. Within this range, the printed material has good resistance, and even when printed on a flexible print medium, problems such as cracking of the coating film are unlikely to occur. More preferably, it is 50-120 degreeC, More preferably, it is 60-100 degreeC, Most preferably, it is 70-90 degreeC.

  When using an acrylic resin together, it is preferable that it is 0.1 to 10 weight% as content with respect to the nonaqueous inkjet ink whole quantity. This range is preferable because printing can be performed without adversely affecting the continuous ejection stability of the ink and without causing mist. More preferably, it is 1-8 weight%, More preferably, it is 1.5-6 weight%.

  Further, when determining the content of the acrylic resin, it is necessary to consider the content of the vinyl chloride-vinyl acetate copolymer resin used together. When both are used in combination, the content of the acrylic resin relative to the addition amount of the vinyl chloride-vinyl acetate copolymer resin is preferably 0.01 to 1, more preferably 0.03 to 0.8. Preferably, it is 0.05-0.6. By being in the above range, it becomes possible to satisfy the continuous discharge stability, the abrasion resistance of the printed matter, and the gloss at a high level.

Specific examples of the acrylic resin suitably used include Mitsubishi Rayon's Dianal (registered trademark) BR-50, BR-52, MB-2539, BR-60, BR-64, BR-73, BR-75, MB-2389, BR-80, BR-82, BR-83, BR-84, BR-85, BR-87, BR-88, BR-90, BR-95, BR-96, BR-100, BR- 101, BR-102, BR-105, BR-106, BR-107, BR-108, BR-110, BR-113, MB-2660, MB-2952, MB-3012, MB-3015, MB-7033, BR-115, MB-2478, BR-116, BR-117, BR-118, BR-122, ER-502;
Paraloid (registered trademark) A-11, A-12, A-14, A-21, B-38, B-60, B-64, B-66, B-72, B-82 manufactured by Dow Chemical , B-44, B-48N, B-67, B-99N, DM-55;
Examples include JONCRYL (registered trademark) 67, 678, 586, 611, 680, 682, 683, 690, 819, JDX-C3000, and JDXC3080 manufactured by BASF.

〔Organic solvent〕
The organic solvent contained in the non-aqueous inkjet ink of the present invention preferably contains any one or more of the solvents represented by the following general formulas (a) to (d).
R ₁ CO (OR ₂ ) _Z OR ₃ (a)
R ₄ CO (OR ₅ ) _Z OCOR ₆ (b)
R ₇ (OR ₈ ) _Z OR ₉ (c)
R ₁₀ COOR ₁₁ (d)

In the above formula, R ₂ , R ₅ and R ₈ are each independently selected from an ethylene group, a propylene group and a butylene group, and R ₁ , R ₃ , R ₄ and R ₆ are each independently carbon. In the alkyl group having 1 to 4, R ₇ and R ₉ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ₁₀ is a 2-hydroxyethyl group, and R ₁₁ is 1 to 8 carbon atoms. Z represents an integer of 1 to 3.

  Among these, it is preferable that the organic solvent represented by (a) and / or (c) is contained, and at least represented by (a) from the viewpoint that the storage stability of ink and the reduction of mist during printing are possible. It is particularly preferable to contain an organic solvent.

  Moreover, it is preferable from a viewpoint of a printing speed improvement to select the organic solvent whose boiling point is 150-200 degreeC, and to make the content into 50 to 98 weight% on the basis of the total weight of non-aqueous inkjet ink.

  As the organic solvent suitably used in the present invention and having a boiling point of 150 to 200 ° C. and represented by the above formula (a) and / or (c), 3-methoxybutanol (boiling point 158 ° C.), diethylene glycol dimethyl ether (boiling point 162) ° C), 3-methylmethoxybutanol (boiling point 174 ° C), diethylene glycol methyl ethyl ether (boiling point 176 ° C), diethylene glycol diethyl ether (boiling point 189 ° C), diethylene glycol methyl isopropyl ether (boiling point 179 ° C), dipropylene glycol dimethyl ether (boiling point 171) ° C), ethylene glycol butyl ether acetate (boiling point 192 ° C), 3-methoxybutyl acetate (boiling point 171 ° C), 3-methyl-3-methoxybutyl acetate (boiling point 188 ° C), and the like. Of these, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, and ethylene glycol butyl ether acetate are preferred from the viewpoint of the storage stability of the ink, and ethylene glycol butyl ether acetate is most preferred.

  Other examples of the organic solvents represented by the formulas (a) to (d) include diethylene glycol methyl butyl ether (boiling point 212 ° C.), diethyl glycol dibutyl ether (boiling point 256 ° C.), triethylene glycol methyl butyl ether (boiling point 261). ° C), tetraethylene glycol dimethyl ether (boiling point 275 ° C), diethylene glycol ethyl ether acetate (boiling point 217 ° C), diethylene glycol butyl ether acetate (boiling point 245 ° C), propylene glycol methyl ether acetate (boiling point 146 ° C), dipropylene glycol methyl ether acetate ( Boiling point 213 ° C), diethylene glycol monobutyl ether (boiling point 230 ° C), dipropylene glycol monomethyl ether (boiling point 190 ° C), dipropylene A glycol monobutyl ether (boiling point 230 ° C.) and the like.

  The organic solvent is preferably contained in an amount of 50 to 98% by weight based on the total weight of the non-aqueous inkjet ink, more preferably 60 to 95% by weight, still more preferably 65 to 90% by weight, and most preferably 70 to 85% by weight. %.

In the present invention, in addition to the organic solvent represented by the above formula, a nitrogen-containing, sulfur-containing, or lactone-based solvent can be used in combination. All of these solvents have a cyclic structure containing an element other than carbon, and when used, the permeability of the ink to the substrate is increased, and the drying property during printing, the abrasion resistance of the printed matter, and the alcohol resistance are increased. Is preferable because of the increase. Examples of nitrogen-containing, sulfur-containing, or lactone solvents that can be used in the present invention include:
A solvent having an oxazolidinone structure such as 3-methyl-2-oxazolidinone and 3-ethyl-2-oxazolidinone;
2-pyrrolidone (γ-butyrolactam), 1-methyl-2-pyrrolidone, 1-ethyl-2-pyrrolidone, γ-valerolactam, γ-hexalactam, γ-heptalactam, γ-octalactam, γ-nonalactam, γ -Lactams such as decaractam, γ-undecalactam, δ-valerolactam, δ-hexalactam, δ-heptalactam, δ-octalactam, δ-nonalactam, δ-decalactam, δ-undecalactam, and ε-caprolactam A solvent having a structure;
γ-butyrolactone, γ-valerolactone, γ-caprolactone, γ-caprolactone, γ-laurolactone, γ-lactone, γ-hexalactone, γ-heptalactone, γ-octalactone, γ-nonalactone, γ-decalactone , Γ-undecalactone, δ-valerolactone, δ-hexalactone, δ-heptalactone, δ-octalactone, δ-nonalactone, δ-decalactone, δ-undecalactone, ε-caprolactone, ε-lactone, etc. Examples of the solvent having a lactone structure include oxygen-containing solvents such as ethylene carbonate, propylene carbonate, and 1,2-butylene carbonate.

  Among these, 3-methyl-2-oxazolidinone (boiling point 266 ° C.), 2-pyrrolidone (γ-butyrolactam) (boiling point 245 ° C.), 1-methyl from the viewpoints of ink permeability to the substrate and drying properties during printing. -2-pyrrolidone (boiling point 202 ° C.), ε-caprolactam (boiling point 267 ° C.), γ-butyrolactone (boiling point 204 ° C.), γ-valerolactone (boiling point 230 ° C.), and ε-caprolactone (boiling point 237 ° C.), propylene carbonate (Boiling point 240 ° C.) is preferred, and 3-methyl-2-oxazolidinone (boiling point 266 ° C.), γ-butyrolactone (boiling point 204 ° C.), and ε-caprolactone (boiling point 237 ° C.) are more preferably selected.

  When a nitrogen-containing, sulfur-containing or lactone solvent is used, the boiling point is preferably 200 ° C to 300 ° C. By setting it as the above range, it is possible to balance the permeability to the base material and the volatility of the solvent, and it is possible to obtain a non-aqueous inkjet ink having a high drying property at the time of printing and an excellent printed material resistance. . Further, it is preferable that the boiling point of the nitrogen-containing, sulfur-containing, or lactone solvent is the highest in the ink. When the ink is dried, highly soluble nitrogen-containing, sulfur-containing or lactone solvents remain until the end, preventing non-volatile components in the non-aqueous inkjet ink from solidifying in the inkjet head, thereby preventing nozzle omission. it can.

  The blending amount of the nitrogen-containing, sulfur-containing or lactone solvent is preferably 1 to 25% by weight based on the total weight of the inkjet ink. If it is this range, favorable drying property is shown and the tolerance improvement of printed matter is anticipated, and it is preferable. More preferably, it is 2 to 20% by weight, still more preferably 4 to 15% by weight, and most preferably 5 to 13% by weight.

  In the present invention, solvents other than those described above can be used in combination for the purpose of adjusting the viscosity and dischargeability of the ink. Specifically, methyl lactate (boiling point 144 ° C.), ethyl lactate (boiling point 154 ° C.), propyl lactate (boiling point 170 ° C.), butyl lactate (boiling point 189 ° C.), N, N-dimethyl-β-butoxypropionamide (boiling point) 216 ° C.), N, N-dibutyl-β-butoxypropionamide (boiling point 252 ° C.) and the like.

[Pigment]
The pigment used in the non-aqueous inkjet ink of the present invention should be appropriately selected from those generally used for printing and paint applications according to the required application such as color development and light resistance. Can do. Moreover, you may use individually by 1 type and may mix and use 2 or more types.

  As the pigment, achromatic pigments such as carbon black, titanium oxide, calcium carbonate, and / or chromatic organic pigments can be used.

  Examples of organic pigments preferably used in the present invention are color index (CI) numbers. I. Pigment Yellow 12, 13, 14, 15, 16, 17, 20, 24, 55, 74, 83, 86, 87, 93, 109, 110, 117, 120, 125, 124, 128, 129, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 170, 171, 172, 174, 176, 180, 185, 188, C.I. I. Pigment orange 16, 36, 43, 51, 55, 59, 61, 64, C.I. I. Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 123, 146, 147, 149, 150, 168, 177, 180, 185, 192, 202, 206, 207, 209, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 245, 269, C.I. I. Pigment violet 19, 23, 29, 30, 37, 40, 50, C.I. I. Pigment blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64, C.I. I. Pigment green 7, 36, C.I. I. Pigment brown 23, 25, 26, C.I. I. Pigment black 1, 6, 7 etc. are mentioned.

  The content of these pigments in the ink is preferably 1 to 15% by weight and more preferably 1 to 8% by weight from the viewpoint of coloring power, storage stability, and inkjet viscosity suitability. When light color ink is used in order to reduce image granularity, the pigment content is preferably 1/10 to 1/2 that of dark ink.

  The average particle diameter (D50) of the pigment in the non-aqueous inkjet ink is preferably 50 to 300 nm. Here, when D50 is 50 nm or more, light resistance and coloring power can be obtained, and when it is 300 nm or less, ink storage stability and continuous ejection stability are stable. The D50 can be measured, for example, by diluting a non-aqueous inkjet ink 200 to 1000 times with ethyl acetate and using MICROTRAC UPA150 manufactured by Nikkiso Co., Ltd. D50 indicates the median diameter.

(Pigment dispersant)
In the present invention, it is preferable to use a pigment dispersant in order to improve the dispersibility of the pigment and the storage stability of the ink. Conventionally known compounds can be used as the pigment dispersant. From the viewpoint of continuous discharge stability and ink storage stability, a resin-type dispersant having a basic functional group is preferred.

  Commercial examples of pigment dispersants include Lubrizol's Solsperse 32000, 76400, 76500, J200, J180, etc .; Big Chemie's Disperbyk-161, 162, 163, 164, 165, 166, 167, 168, etc .; Ajinomoto Fine Techno Co., Ltd. Ajisper PB821, PB822 etc. are mentioned.

  The weight average molecular weight (hereinafter referred to as Mw) of the pigment dispersant is preferably 5,000 to 20,000, and more preferably 10,000 to 20,000. When Mw is 5,000 or more, the stability of the pigment dispersion is improved because the stability of the pigment dispersant itself in the organic solvent used in the ink is good. When it is 20,000 or less, the compatibility with the binder resin is good, the whitening phenomenon of the ink coating is suppressed, and the color development is good.

Furthermore, the pigment dispersant preferably has a ratio (Mw / Mn) of a weight average molecular weight (Mw) to a number average molecular weight (hereinafter Mn) determined by GPC of 1 to 2, and Mw / Mn is 1 to 2. More preferably, 1 to 1.8 is particularly preferable.
By setting Mw / Mn to 2 or less, a pigment dispersion with little variation in the particle diameter of the pigment can be obtained, and it is possible to achieve both low viscosity and storage stability of the pigment dispersion.

  The Mw and Mn can be obtained as styrene-converted molecular weight by general gel permeation chromatography (hereinafter referred to as GPC). For example, using TSKgel column (manufactured by Tosoh Corporation), GPC (manufactured by Tosoh Corporation, HLC-8320GPC) equipped with an RI detector can be represented by polystyrene equivalent molecular weight when DMF is used as a developing solvent.

    5-20 are preferable and, as for the acid value (mgKOH / g) of the pigment dispersant used suitably by this invention, 5-15 are more preferable. The amine value (mgKOH / g) is preferably 5 to 50, more preferably 20 to 45, and particularly preferably 25 to 40. When the acid value and amine value of the pigment dispersant are within the above ranges, in the pigment dispersion step, the time until the viscosity of the pigment dispersion becomes low enough to be suitable for an inkjet ink is shortened. It is preferable because storage stability is improved. In addition, the said acid value can be calculated | required similarly to the case of an acrylic resin. The “amine value” represents an amine value per 1 g of the solid content of the dispersant, and is a value converted to an equivalent of potassium hydroxide after being determined by potentiometric titration using a 0.1N hydrochloric acid aqueous solution.

[Pigment derivative]
A pigment derivative can also be used in the ink of the present invention. The pigment derivative is used for the purpose of enhancing the adsorptivity between the dispersant and the pigment and improving the storage stability. As the pigment derivative, a compound having an acidic group such as a sulfonic acid group or a carboxyl group in the organic pigment residue is preferably used.

  The content of the pigment derivative is preferably from 0.1% by weight to 20% by weight, particularly preferably from 1% by weight to 15% by weight, based on the pigment. When the content is 0.1% by weight or more, stability and color developability are improved, and when the content is 20% by weight or less, the viscosity of the ink is finished in a suitable range and storage stability is improved, which is preferable.

〔Additive〕
The ink of the present invention has various surface modifiers, slip agents, plasticizers, UV inhibitors, light stabilizers, antioxidants, hydrolysis inhibitors, rust inhibitors, etc., in order to enhance printability and printed matter resistance. Additives can be used.

  Examples of the surface conditioner include silicon-based, fluorine-based, acrylic-based, and acetylene glycol-based, among which silicon-based is preferable. Among silicon-based surface conditioners, a modified polysiloxane compound in which an organic group is introduced into part of the methyl group of dimethylpolysiloxane is preferable. Examples of modification include polyether modification, methylstyrene modification, alcohol modification, alkyl modification, aralkyl modification, fatty acid ester modification, epoxy modification, amine modification, amino modification, mercapto modification, etc., and are polyether modification and aralkyl modification. It is preferable in terms of continuous discharge stability and the like, and aralkyl modification is particularly preferable in terms of continuous discharge stability and ink drying properties.

Examples of polyether-modified polysiloxane compounds include, for example, KF-353A, KF-354L, KF6017, X-22-6551, AW-3 manufactured by Shin-Etsu Chemical Co., Ltd., SAG001, SAG002 manufactured by Nissin Chemical Industry Co., Ltd. , SAG003, SAG005, SAG503A, SAG008, SAG010, 8019ADDITIVE, 8029ADDITIVE, 8054ADDITIVE, 8526ADDIZIVE, 8616DIDIVITE, 57ADDITL, FAD -BYK-300, 302, 30 manufactured by Japan , 307,330,377, TEGO made of Evonik Degussa Glide 100,110,130,406,410,415,420,432,435,440,450;
Examples of aralkyl-modified polysiloxane compounds include BYK-322 and 323 manufactured by Big Chemie Japan, KF-410 manufactured by Shin-Etsu Chemical Co., Ltd., manufactured by Toray Dow Corning Co., Ltd. SM 7001EX, SM 7002EX and the like.
As described above, among these materials, BYK-322 and 323, which are aralkyl-modified polysiloxane compounds, are particularly preferably used.

  The content of the surface conditioning agent is preferably 0 to 2% by weight, preferably 0.001 to 1% by weight, based on the total weight of the non-aqueous inkjet ink, and 0.01 to 0.5% by weight. % Is more preferable.

〔recoding media〕
The recording medium used in the present invention is not particularly limited, and a plastic substrate such as soft PVC, hard PVC, polystyrene, polystyrene foam, PMMA, polypropylene, polyethylene, PET, polycarbonate, or a mixed or modified product thereof, fine paper, Examples thereof include paper base materials such as art paper, coated paper and cast coated paper, and metal base materials such as glass and stainless steel. Among these, from the viewpoint of price and workability, as described above, soft PVC and hard PVC which are non-absorbent substrates are preferably used.

[Ink production method]
The ink of the present invention can be produced by a known method. Specifically, first, after mixing a single or mixed organic solvent, pigment, and a binder resin, a dispersant, etc. when blended, a paint shaker, a sand mill, a roll mill, a medialess disperser, etc. The pigment dispersion is prepared by dispersing the pigment. To the obtained pigment dispersion, the remainder of the organic solvent, the remainder of the binder resin, and other additives (for example, a surface conditioner) are added so as to have desired ink properties, and after the binder resin is dissolved, It can be obtained by removing coarse particles with a filter or the like.

[Physical properties of inkjet ink]
The non-aqueous inkjet ink of the present invention preferably has a surface tension at 25 ° C. of 20 mN / m or more and 50 mN / m or less from the viewpoint of the balance between the ejectability from the inkjet head and the reliability of dot formation after landing. 25 mN / m or more and 40 mN / m or less is more preferable. From the same viewpoint, the viscosity at 25 ° C. is preferably 2 mPa · s or more and 20 mPa · s or less, and more preferably 5 mPa · s or more and 15 mPa · s or less.
The surface tension can be measured by confirming the surface tension when the platinum plate is wetted with ink in an environment of 25 ° C. using an automatic surface tension meter CBVP-Z manufactured by Kyowa Interface Science Co., Ltd. it can. The viscosity can be measured by reading the viscosity at 50 rpm in a 25 ° C. environment using a TVE25L viscometer manufactured by Toki Sangyo Co., Ltd.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not specifically limited to an Example. In the following description, “parts” and “%” represent “parts by weight” and “% by weight”, respectively, unless otherwise specified.

[Production of vinyl chloride-vinyl acetate copolymer resin A]
After replacing the inside of the pressure vessel equipped with a stirrer, thermometer and nitrogen gas inlet with nitrogen, 750 parts of deionized water, 290 parts of vinyl acetate, 20 parts of sodium dodecylbenzenesulfonate as an emulsifier, polyoxyethylene as a chain transfer agent 20 parts of nonylphenyl ether was added. Subsequently, after the inside of the container was depressurized and 700 parts of vinyl chloride was added, the temperature was raised to 60 ° C. while stirring. After dropwise addition of a solution prepared by dissolving 5 parts of ammonium persulfate in 100 parts of deionized water as a polymerization initiator, the reaction is performed for 20 hours while maintaining the temperature inside the container at 60 to 70 ° C, and then cooled to 30 ° C. This terminated the polymerization. 1800 parts of 1M sodium chloride aqueous solution was added little by little to the reaction solution, and the resulting precipitate was filtered off, and then washed with deionized water three times to give a vinyl chloride-vinyl acetate copolymer resin A. Got.

[Production of vinyl chloride-vinyl acetate copolymer resins BK]
Vinyl chloride-acetic acid is the same as vinyl chloride-vinyl acetate copolymer resin A except that the amount of chain transfer agent, the amount of vinyl chloride, and the amount of vinyl acetate are changed to those shown in Table 1 below. Vinyl copolymer resins B to K were produced.

  Table 1 also shows the specifications of VINNOL E15 / 45TF (emulsion polymer manufactured by Wacker Chemie) and Solvine CL (suspension polymer manufactured by Nissin Chemical Industry) used in Examples described later. In Table 1, | M | is the absolute molecular weight, | Mw | is the weight average absolute molecular weight, and | Mn | is the number average absolute molecular weight.

(Production example of pigment dispersion)
20 parts of Pigment Blue 15: 4 as a pigment, 7 parts of Solsperse J200 as a pigment dispersion resin and 73 parts of ethylene glycol butyl ether acetate were mixed and predispersed with a disper, and then filled with 1800 g of zirconia beads having a diameter of 0.5 mm. The dispersion was performed for 2 hours using a 0.6 L dyno mill to obtain a pigment dispersion.

Example 1
20 parts of pigment dispersion, 5.4 parts of vinyl chloride-vinyl acetate copolymer resin, JONCRYL586 (BASF styrene-acrylic copolymer resin, weight average absolute molecular weight 4000, 1.4 parts of glass transition point 60 ° C., acid value 108 mgKOH / g), Dianal BR-113 (Mitsubishi Rayon acrylic resin, weight average absolute molecular weight 35000, glass transition point 75 ° C., acid value 3.5 mg KOH / g) ), 0.36 parts of ethylene glycol butyl ether acetate, and 7.5 parts of γ-butyrolactone were sequentially added while stirring with a disper and stirred until sufficiently uniform. Thereafter, filtration was carried out with a membrane filter having an opening of 1.0 μm to remove coarse particles that cause clogging of the head, and the ink-jet ink of the present invention was prepared.

(Examples 2 to 13, Comparative Examples 1 to 6)
Non-aqueous inkjet inks of Examples 2 to 13 and Comparative Examples 1 to 6 were produced in the same manner as Example 1 except that the materials shown in Table 2 below were used.

The abbreviations used in Table 2 are as follows.
・ BGAc (ethylene glycol monobutyl ether acetate, boiling point 192 ° C.)
GBL (γ-butyrolactone, boiling point 204 ° C.)
ECL (ε-caprolactone, boiling point 237 ° C.)

(Print evaluation)
The obtained ink-jet ink was filled in a wide format ink-jet printer (ColorPainter 64S manufactured by Seiko I Infotech Co., Ltd.), and printing evaluation was performed using a polyvinyl chloride sheet (MD-5 manufactured by Metamark Co., Ltd.) as a printing medium.

(Continuous discharge stability evaluation)
A 10 m ² solid was printed on the print medium at a speed of 30 m ² / h, and a nozzle check pattern was printed to confirm the number of missing nozzles. The evaluation criteria were as follows, and B or higher was considered good.
A: 0 missing nozzles after printing B: 3 missing nozzles after printing C: 7 missing nozzles after printing D: 20 missing nozzles after printing E: 20 missing nozzles after printing

(Deflection evaluation)
A 10 m ² solid was printed on the print medium at a speed of 30 m ² / h, a nozzle check pattern was printed, and it was confirmed whether the droplets of the inkjet ink had landed at a desired position. The evaluation criteria were as follows, and B or higher was considered good.
A: No deviation of inkjet ink droplets is observed even by microscopic observation. B: No deviation of inkjet ink droplets is observed visually. C: Inkjet ink droplet deviation is observed visually.

(Evaluation of alcohol resistance)
Alcohol resistance was evaluated by rubbing a printed material on which a single-color solid was printed on a printing medium at a speed of 4 m ² / h with a cotton swab dipped in an aqueous ethanol solution. The concentration of the aqueous alcohol solution was changed, the color transfer of the ink coating to the cotton swab was confirmed, and the following criteria were evaluated.
A: No color transfer to cotton swabs with 80% ethanol solution B: No color transfer to cotton swabs with 60% ethanol solution C: Color transfer to cotton swabs with 60% ethanol solution

(Gloss evaluation)
About the solid printed matter which printed on the printing medium at a speed | rate of 4 m < ² > / h, 60 degree glossiness was measured using the glossiness meter (BYK company micro tri-gloss). The evaluation criteria were as follows, and B or higher was considered good.
A: Glossiness of 70 or more B: Glossiness of 50 to 70
C: Glossiness 30-50
D: Glossiness less than 30

(Storage stability evaluation)
The viscosity of the prepared ink was measured using an E-type viscometer (TVE-20L manufactured by Toki Sangyo Co., Ltd.) at 25 ° C. under the condition of a rotation speed of 50 rpm. This ink was stored in a thermostat at 70 ° C. and accelerated with time, and the change in the viscosity of the ink before and after aging was evaluated. The evaluation criteria were as follows, and B or higher was considered good.
A: Viscosity change rate after storage for 6 weeks is less than ± 10% B: Viscosity change rate after storage for 6 weeks is less than ± 10-20% C: Viscosity change rate after storage for 6 weeks is ± 20% or more

(Evaluation results)
The results of the above evaluation tests are shown in Table 2 above.

  As shown in Table 2, the binder resin has a weight average absolute molecular weight (| Mw |) of 20,000 to 40,000, and a ratio of the weight average absolute molecular weight to the number average absolute molecular weight (| Mn |) ( | Mw | / | Mn |) is a vinyl chloride-vinyl acetate copolymer resin having a value of 1.3 or more and 2.2 or less, and the evaluation regarding printability such as continuous ejection stability and deflection is good. High quality prints could be obtained. On the other hand, in the comparative example, an ink satisfying printability and print quality could not be obtained.

Claims (5)

A non-aqueous inkjet ink containing an organic solvent, a pigment, and a vinyl chloride-vinyl acetate copolymer resin,
The vinyl chloride-vinyl acetate copolymer resin has a weight average absolute molecular weight (| Mw |) of 20,000 to 40,000, and a ratio of the weight average absolute molecular weight to the number average absolute molecular weight (| Mn |). (| Mw | / | Mn |) is 1.3 or more and 2.2 or less,
A non-aqueous inkjet ink, wherein the vinyl chloride-vinyl acetate copolymer resin is an emulsion polymer of a vinyl chloride monomer and a vinyl acetate monomer.   The vinyl chloride-vinyl acetate copolymer resin does not contain a resin having an absolute molecular weight (| M |) of 200,000 or more, or 10% by weight or less based on the total resin. Non-aqueous inkjet ink. The non-aqueous inkjet ink according to claim 1, wherein the organic solvent contains any one or more of solvents represented by general formulas (a) to (d).
R ₁ CO (OR ₂ ) _Z OR ₃ (a)
R ₄ CO (OR ₅ ) _Z OCOR ₆ (b)
R ₇ (OR ₈ ) _Z OR ₉ (c)
R ₁₀ COOR ₁₁ (d)
(Wherein R ₂ , R ₅ , and R ₈ are each independently selected from an ethylene group, a propylene group, and a butylene group,
R ₁ , R ₃ , R ₄ and R ₆ are each independently an alkyl group having 1 to 4 carbon atoms,
R ₇ and R ₉ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms,
R ₁₀ is a 2-hydroxyethyl group,
R ₁₁ is an alkyl group having 1 to 8 carbon atoms,
Z represents an integer of 1 to 3. )   The non-aqueous inkjet ink according to claim 1, wherein the organic solvent further contains a nitrogen-containing, sulfur-containing, or lactone solvent.   The non-aqueous inkjet ink according to claim 1, further comprising a pigment dispersant.